Re: [Autoconf] Updated ad hoc addressing model document

["Teco Boot" <[e-mail]>]

Hi Charlie,

>> Up to now, all IP addressing models I am aware of provide 1-hop L3
>> communication between nodes that have L2 connectivity.
>>
>
>If I get your point, what you mean is that when two nodes
>share a link, they can use L3 protocols to communicate.
>
>As far as I understand it, the addressing model does not
>change this.  IP supports point-to-point communication
>between such "adjacent" nodes.
>
>How adjacency is discovered is usually considered
>out of scope.  Either subnet prefixes are "assigned"
>(suddenly, it doesn't look like a Manet anymore)
>or "discovered" (oops, we're running new protocols)
>or "assumed".  In the latter case, you'd better make
>your assumptions minimal, or else (protocol-wise)
>you are moving back into traditional a fixed network
>model.  I know it's nicer there and all.

Thanks for this analysis.


>> The proposed addressing model for MANETs breaks this. Now there
>> is a need for something clever. This clever thing could be
>> stopped.
>>
>
>I do not agree with this.  See above.

It is fact of life that the "clever thing could be stopped".
And existing IP addressing models don't depend on such clever 
thing. Here, we have the "assumption". Right?


>               I also do not
>agree that we must avoid being clever.

Agreed. That is why I use an addressing model that is better resistant
against failures.


>       However,
>I agree that simpler is better, all the while adhering
>to Einstein's famous dictum.
>
>> There is no reason not using link-locals for 1-hop traffic.
>> If you say this is a particular and specific setup, is this a
>> qualification for IPv6?
>> If not, what are you referring to?
>>
>
>I read this, and had to smile.  Of course there's no reason
>to avoid link-locals for 1-hop traffic as long as you _know_
>it's one hop.  In fact, blast away.

OK, now we are there.
MANET protocols that use RFC5498 can perfectly use link-locals.
Same for L2 address resolving, as ND does.


>But for people who are running networks without such
>comforts, assurance of availability for a L2 communication
>channel is often necessary or at least highly desirable.
>Then suddenly your link-local address is potentially
>(a) invalid (b) unavailable or (c) ambiguous.  These
>are normally considered poor indicators for IP-based
>communications.

What happens if your ULA or global is (a) invalid,
(b) unavailable or (c) ambiguous? 
I don't see a difference with link-locals.
Link-locals are used for protocols that require 1-hop
communication or when no other addresses are available.
In the latter, it is also 1-hop only.


>And that is the problem needing solution in the
>general case, which has motivated the current form
>of the addressing model document.

With IPv6 in mind, the general case can easily include
link-locals. Wouldn't it be nice to support IPv6 basics?


Regards, Teco